[wasm][turbofan] Match operators to node representation

This fixes operators in wasm Turbofan that were mixing up integer sizes
and pointers with tagged pointers.

Additional changes:
- Remove unused (and non-compiling if V8_MAP_PACKING)
  GraphAssembler::StoreMap.
- Factor out WasmGraphBuilder::IsNull.

Change-Id: I9d99827e35507adc0af391bd39975d55371b98cf
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3306981Reviewed-by: Nico Hartmann <nicohartmann@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Manos Koukoutos <manoskouk@chromium.org>
Cr-Commit-Position: refs/heads/main@{#78196}

src/compiler/graph-assembler.cc

@@ -578,15 +578,6 @@ TNode<Map> GraphAssembler::LoadMap(Node* object) {
 #endif
 }
 
-void GraphAssembler::StoreMap(Node* object, TNode<Map> map) {
-#ifdef V8_MAP_PACKING
-  map = PackMapWord(map);
-#endif
-  StoreRepresentation rep(MachineType::TaggedRepresentation(),
-                          kMapWriteBarrier);
-  Store(rep, object, HeapObject::kMapOffset - kHeapObjectTag, map);
-}
-
 Node* JSGraphAssembler::StoreElement(ElementAccess const& access, Node* object,
                                      Node* index, Node* value) {
   return AddNode(graph()->NewNode(simplified()->StoreElement(access), object,

src/compiler/graph-assembler.h

@@ -278,7 +278,6 @@ class V8_EXPORT_PRIVATE GraphAssembler {
   TNode<Map> UnpackMapWord(Node* map_word);
 #endif
   TNode<Map> LoadMap(Node* object);
-  void StoreMap(Node* object, TNode<Map> map);
 
   Node* DebugBreak();
 

src/compiler/wasm-compiler.h

@@ -691,6 +691,8 @@ class WasmGraphBuilder {
   // generates {index > max ? Smi(max) : Smi(index)}
   Node* BuildConvertUint32ToSmiWithSaturation(Node* index, uint32_t maxval);
 
+  Node* IsNull(Node* object);
+
   using BranchBuilder = std::function<void(Node*, BranchHint)>;
   struct Callbacks {
     BranchBuilder succeed_if;